An ionic liquid is a salt composed of an organic cation of a hetero ring and an inorganic anion. Although NaCl, a representative inorganic salt, has to be melted at a temperature of 800° C. or higher, an ionic liquid typically has a low melting point of 100° C. or less.
An ionic liquid is less toxic than general organic solvents, and has almost no vapor pressure, and is thus non-volatile. Moreover, an ionic liquid may efficiently dissolve inorganic and organic chemicals because of the strong polarity thereof, and is thus receiving attention as a green solvent capable of replacing organic solvents. Ionic liquids have high ionic conductivity, a wide electrochemical range, and high thermal stability. By virtue of the superior properties thereof, ionic liquids have been utilized in a variety of fields, including those of secondary battery electrolytes, catalysts, liquid-liquid extraction solvents, carbon dioxide capture, thermal fluids, etc. Furthermore, ionic liquids are advantageous because the properties of the ionic liquids may vary depending on changes in the size and structure of cations and anions, making it possible to design an ionic liquid so as to be suitable for an industrial-processing end use through various combinations of two ions. Hence, thorough research thereon by institutes and companies is ongoing.
Recently, a high-purity ionic liquid is used to purify a material such as an organic material. During the purification, when the ionic liquid contains impurities or is denatured, the purification performance thereof may deteriorate, and thus there is a need for a novel ionic liquid or a high-purity purification process.
However, high-purity purification of the ionic liquid requires an additional purification system and method, considerably increasing processing costs, which is undesirable.
Therefore, it is necessary to develop a novel technique for purifying an ionic liquid, which contains impurities or is denatured, to high purity in a simple manner and reusing the same.